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Vibration level characterization from a needle gunused on U.S. naval vesselsScott E. DunnUniversity of South Florida

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Scholar Commons CitationDunn, Scott E., "Vibration level characterization from a needle gun used on U.S. naval vessels" (2006). Graduate Theses andDissertations.http://scholarcommons.usf.edu/etd/2512

Vibration Level Characterization from a Needle Gun Used on U.S. Naval Vessels

by

Scott E. Dunn

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Public Health

Department of Environmental and Occupational Health College of Public Health

University of South Florida

Major Professor: Thomas E. Bernard, Ph.D. Steve Mlynarek, Ph.D.

Andrea Spehar, D.V.M, M.P.H., J.D.

Date of Approval: July 14, 2006

Keywords: hand-arm vibration, needle gun, needle scaler, percussive tool, vibration white finger

© Copyright 2006, Scott E. Dunn

Acknowledgments

Foremost, I would like to acknowledge the United States Navy for providing the

opportunity for pursuing my advanced degree. Especially, I want to thank the senior officers

within the Medical Service Corps that had the confidence in selecting me for this DUINS

assignment which ultimately allowed me to pursue my education interests at the University

of South Florida. I would also like to thank the Naval Medical Education and Training

Command staff that supported me throughout the program.

I would like to thank my committee members for their time, consideration, and effort

during the development and completion of my research. I would like to thank Dr. Andrea

Spehar for becoming a committee member on such short notice and providing an “outsider”

perspective on the project. Dr. Steve Mlynarek was an excellent sounding board for ideas

and problem solving and kept me on track with this project and my coursework at the

University of South Florida. I would especially like to thank Dr. Tom Bernard for his time,

effort, and his expertise on the subject of this research.

I would like to thank the commanding officer and the Operations Department

personnel of the USS McInerney (FFG-8), home-ported in Mayport, Florida, for their

cooperation in allowing me to conduct my research on their vessel and use the personnel to

conduct the research. I would also like to acknowledge LT John Zumwalt at DESRON 14

and LCDR Tim Jirus at SERMC in Mayport for their assistance and coordination of the

research on USS McInerney.

On a personal level, I am grateful to my wife Beth and my children, Kathryn, Jeffrey,

and Ryan that provided support, love, and understanding throughout this program. I would

also like to thank the following individuals who assisted me with my research: Adam Marty,

LT Charles Wilhite, and Luis Pieretti.

i

Table of Contents

List of Tables ii List of Figures iii Abstract iv Symbols and Abbreviations vi Introduction 1 Literature Review 5 Background 5 Health Effects of Hand-Transmitted Vibration 6 Diagnosis of Hand-Transmitted Vibration 8 Physics and Terminology 9 Occupational Standards and Guidelines for Hand-Transmitted Vibration 14 Hand-Transmitted Vibration Measurements 20 Studies Associated with Needle Scalers and Hand-Transmitted Vibration 22 Study Objectives 24 Methods 25 Materials & Equipment 25 Vibration Measurement Instrumentation 26 Protocol 27 Results 29 Discussion and Conclusions 31 References Cited 35 Appendix A: PCB ICP Accelerometer Specifications 39

Appendix B: Taylor Needle Scaler T-7356 Specifications 41

ii

List of Tables

Table 1 Taylor–Pelmear Stages of VWF 9 Table 2 Stockholm Workshop Scale for the Classification of Cold-Induced

Raynaud’s Phenomenon in HAVS 9 Table 3 Stockholm Workshop Scale for the Classification of Sensorineural Affects

of HAVS 9 Table 4 Needle Gun Vibration Measurements from HSE Contract Research Report

234/199 23 Table 5 Order Exposure 29 Table 6 Summary of ahv for All Subjects, Trials, Pressure (60 & 80 PSI), and

Contact/No Contact 30

iii

List of Figures Figure 1 Description of Biodynamic and Basicentric Orthogonal Coordinate Axis

Systems 12 Figure 2. Frequency Weighting Used by ANSI, ISO and ACGIH 13 Figure 3. ANSI Health Risk Zones for DEAV and DELV 17 Figure 4. Taylor Pneumatic Tool Company, Needle Scaler, Model T-7356 25 Figure 5. Illustration of Accelerometer Mounting 26

iv

Vibration Level Characterization from a Needle Gun Used on U.S. Naval Vessels

Scott E. Dunn

ABSTRACT

United States (U.S.) Navy sailors are exposed to a very large number of hazards,

both chemical and physical. Occupational vibration from pneumatic air tools is one of

the potential exposure hazards. There are very limited data as to the exposures to one

type of tool, a needle gun or needle scaler, used by the sailors.

The purpose of this study was to characterize the vibration levels generated by a

needle gun used in the U.S. Navy. The design of the study evaluated the difference

pressure had on the acceleration levels generated from the needle scaler. Five subjects

were used in the evaluation of the tool. Each subject was required to hold the tool for

twenty seconds activated without contact and activated on a surface and at two different

pressures, 60 and 80 pound per square inch (psi). Each subject repeated each of the

conditions three times for a total of 12 measurements. Each subject was also required to

hold the tool in hand without the tool activated. The measurements were collected from

an accelerometer on the needle gun following ISO 5349-1:2001 and ISO 5349-2:2001

methods.

Significant differences were observed individually in pressure (p<0.0001),

contact (p<0.0001)), and subjects (p<0.001). In addition, there was a significant

interaction between contact and pressure (p<0.001). It was concluded that U.S. Navy

v

sailors are not likely at significant risk to Hand-Arm Vibration Syndrome for lifetime

exposures to hand transmitted vibration.

vi

SYMBOLS AND ABBREVIATIONS ahw(t) instantaneous single-axis acceleration value of the ISO frequency-

weighted hand-transmitted vibration at time t, in meters per second squared (m/s2);

ahw root-mean-square (rms) single-axis acceleration value of the ISO

frequency-weighted hand-transmitted vibration, in m/s2

ahwx, ahwy, ahwz values of ahw, in m/s2, for the axes denoted x, y and z respectively ahv vibration total value of the ISO frequency-weighted rms acceleration;

it is the root-sum-of squares of the ahw values for the three measures axes of vibration in m/s2

ahv(eq, 8h) daily vibration exposure (8-h energy equivalent vibration total value),

in m/s2

ahv(DEAV) vibration total value for a time Tv other than 8 h that will result in a

DEAV of 2.5 m/s2

ahv(DELV) vibration total value for a time Tv other than 8 h that will result in a

DELV of 5.0 m/s2

A(8) a convenient alternative term for the daily vibration exposure ahv(eq, 8h) DEAV or EAV Daily Exposure Action Value – A(8) is equal to 2.5 m/s2

DELV or ELV Daily Exposure Limit Value – A(8) is equal to 5.0 m/s2

Dy group mean total (lifetime) exposure duration, in years HAVS Hand-arm vibration syndrome HTV Hand-transmitted vibration rss root sum of squares – the square root of the sum of the squares of the

x, y, and z axes. T total daily duration of exposure to the vibration ahv T0 reference duration of 8 h (28,800 s) Wh frequency-weighting characteristic for hand-transmitted vibration

1

INTRODUCTION

The general United States worker may be exposed to a myriad of hazards, both

physical and chemical. Occupational vibration is one of the many physical hazard

exposures. It is found in landscaping (mowing lawns and trimming shrubs), tree cutting,

driving heavy construction equipment, or using any assortment of hand power tools (i.e.,

jackhammers, grinders, needle guns, etc.) (NIOSH, 1989). Eight to ten million

Americans are exposed to occupational vibration where two million of these are exposed

to hand-arm vibration alone (Wasserman, 2001).

Occupational vibration is categorized into hand-arm vibration (HAV) and whole

body vibration (WBV). “Whole body vibration affects the entire human body, and is

usually transmitted in a sitting or standing position from a vibrating seat or platform”

(Wilder, D. E. Wasserman, J. Wasserman, 2002, p. 80). Hand-arm vibration focuses on

the hand-arm unit alone and is transmitted to the hand via a power tool (Wilder et al.,

2002).

Hand-arm and whole-body vibration each elicit different health effects (Wilder et

al., 2002). Whole body vibration primarily affects the lower back region (Wilder et al.,

2002). The primary health effect currently associated with hand-arm Hand-Arm

Vibration Syndrome (HAVS)(Wilder et al., 2002). Vibration white finger is also known

by other names, such as vibration-induced Raynaud’s phenomenon (Pelmear, Taylor &

Wasserman, 1992), secondary Raynaud’s phenomenon (Griffin, 1990), Raynaud’s

Phenomenon of Occupational Origin, and vibration white finger (VWF) (Bruce,

2

Bommer, & Moritz, 2003). The prevalence and severity of HAVS usually increases with

the magnitude of acceleration of the power tool and the duration of time the tool is used

(NIOSH 1989).

United States Navy sailors, like their American worker counterparts, are exposed

to hand-transmitted vibration (C. R. Wilhite, personal communication, July 12, 2006). A

typical example is the use of a compressed air power tool called a needle gun or needle

scaler. The needle scalers are used to remove rust and/or coatings from the substrate,

usually a steel bulkhead, deck or railing. Needle scalers are used extensively during

periods when the ship was in port.

The exposure levels to these tools have not been fully characterized and the

exposure levels are unknown. In 1999, Paddan, Haward, Griffin, & Palmer published

some limited hand transmitted vibration data on several tools from surveys conducted

around the United Kingdom. They conducted sampling on three needle scalers and found

a range between 10.9 to 28.7 meters per second per second (m/s2) (Paddan et al., 1999).

Currently, the U.S. does not have a regulatory standard for occupational vibration.

However, the U.S. has three health and safety guidance documents published by:

American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit

Value (TLV) for Hand-Arm Vibration (2006), the American National Standards Institute

(ANSI) S2.70-2006 American National Standard Guide for the Measurement and

Evaluation of Human Exposure to Vibration Transmitted to the Hand (2006), and the

National Institute for Occupational Safety and Health (NIOSH) Criteria For a

Recommended Standard: Occupational Exposure to Hand-Arm Vibration (1989). The

international community also has published similar guidelines:

3

• International Standards Organization (ISO) 5349-1:2001 Mechanical vibration - Guidelines for the measurement and the assessment of human exposure to hand-transmitted vibration (2001).

• European Directive 2002/44/EC - On the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (vibration)(2002).Member states were required to comply with the Directive by 6 July 2005.

The occupational exposure limits published by most of the standards are prefaced

with a disclaimer indicating that the “etiology of these disorders is not well [understood]”

(ANSI S3.34-1986, 1986, p. 1). ANSI’s older hand-transmitted vibration standard (1986)

goes on to state “that because of several confounding factors, Appendix B [of ANSI

S3.34-1986, Latent Period for Hand-Transmitted Vibration] shall not be construed to be a

general guide to permissible exposures to vibration transmitted to the hand” (p. 1).

NIOSH (1989) indicates that there are many variables that affect the acceleration of the

transmitted vibration to the hand and therefore has not established a recommended

exposure limit. The ISO 5349-1 (2001) publication states that the standard “does not

define the limits of safe vibration exposure” (p. 1) and therefore does not provide an

exposure limit.

The European Directive (2002), ACGIH TLV for Hand-Transmitted Vibration

(2006), and the new ANSI S2.70 standard (2006) have established an occupational

exposure limit for hand-transmitted vibration. The European Directive for occupational

vibration (2002) suggests a numerical value for vibration with the exposure action limit

(EAL) of 2.5 m/s2 (rms) and an exposure limit value (ELV) of 5.0 m/s2 (rms). The

European Directive (2002) derived these values from the ISO 5349 (1986) standard. The

ANSI S2.70 (2006) standard defines the daily EAV “represents the health risk threshold

4

to hand-transmitted vibration (p. 11).” At the EAV and above, abnormal signs &

symptoms will become prevalent. The daily ELV is considered a high health risk and the

prevalence of symptoms will be more prevalent in the exposed population (ANSI, 2006).

The new ANSI S2.70 standard (2006) for hand-transmitted vibration has also adopted the

same European Directive (2002) ELV and EAV.

The current ACGIH TLV for Hand-Transmitted Vibration (2006) is similar to the

ISO 5349 (1986) hand-transmitted vibration standard. The ACGIH TLV for hand-

transmitted vibration (2006) is based on the dominant frequency-weighted, single axis

acceleration and on a four hour exposure. The ANSI S2.70 (2006) and the European

Directive (2002) vibration levels are based on an equal energy model (root sum of

squares for each of the orthogonal axes of the hand) and standardized to an eight hour

exposure.

5

LITERATURE REVIEW

Background

At the beginning of the 20th century, physicians began to document health effects

generated from vibrating equipment/tools. One of the first documented occurrences of

occupational injury from vibration appeared in 1907 when the United Kingdom

Departmental Committee on Compensation for Industrial Diseases identified “neurosis”

(p.74) in workers that was caused by vibration from pneumatic tools (Griffin, 1997). In

1911, the Italian physician, Giovanni Loriga, identified Raynaud’s phenomenon in

workers that used pneumatic hammers on stone and marble (Bovenzi, 1998a). And in the

United States, Alice Hamilton observed Raynaud’s phenomenon caused by vibration of

pneumatic tools used in stone cutting in 1918 (Pelmear et al., 1992). In 1960, Louis

Pecora et al. (1960) stated “that Raynaud’s phenomenon of occupational origin may not

be completely eradicated but that it may have become an uncommon occupational disease

approaching extinction in [the United States]” (p. 82).

From the time occupational vibration was first identified as a health hazard, more

and more sources of hand-transmitted vibration have been identified. Besides vascular

related adverse health effects (e.g., VWF), other conditions have been linked to hand-

transmitted vibration, which include sensineural and musculoskeletal effects (Pelmear et

al., 1992). Since the turn of the twentieth century, the scientific community has

commonly assumed the vibration frequency range of significance is between 8 – 1000 Hz

(Griffin, 1990).

6

Health Effects of Hand-Transmitted Disorders

The ANSI S2.70 standard (2006) defines hand-transmitted vibration as “the

mechanical vibration that, when transmitted to the human hand-arm system, may entail

risks to worker health and safety, in particular vascular, bone or joint, neurological and

muscular”[disorders] (p. vi). Hand-transmitted vibration is vibration that is transmitted to

the hand by some type of rotating and/or percussive hand held tool (Bovenzi, 1998a).

Workers that use rotating and/or percussive tools are found in mining, construction,

forestry, shipbuilding, and landscaping, among others (ISO 5389-1, 2001).

The target organs for hand-transmitted vibration using hand-held power tools

include the skin vasculature of the fingers, sensory nerves of the hand, and components of

the “locomotor apparatus of the hand-arm system" (Pelmear et al., 1992). The primary

health effect currently associated with hand-transmitted vibration is vibration white finger

(VWF), Raynaud’s phenomenon of occupational origin, or hand-arm vibration syndrome

(HAVS) (Pelmear et al., 1992). The prevalence of hand-arm vibration syndrome

(HAVS) in the U.S. for worker populations that use vibrating tools ranges from 6 to

100% with an average of about 50% (NIOSH, 1989). There are also other disorders

associated with hand-transmitted vibration from different types of tools other than

vascular disorders (VWF). Griffin separates the disorders into five separate categories:

vascular disorders, bone and joint disorders, peripheral neurological disorders, muscle

disorders, and other disorders (e.g., of the whole-body and central nervous system)

(Griffin, 1990).

Vibration white finger is the commonly known health effect associated with hand-

transmitted vibration. Environmental factors can increase the prevalence of this disorder.

7

Bovenzi (1998b) demonstrated that different geographic areas are more or less susceptible

to VWF based on temperature. Colder climates had a higher prevalence of VWF compared

to warm climates (Bovenzi, 1998b). Symptoms associated with VWF include tingling,

numbness, blanching of the fingers, cyanosis (a bluish or purplish discoloration due to

deficient oxygenation of the blood) and gangrene (Griffin, 1990).

The actual HAVS mechanisms caused by hand-transmitted vibration are not clear

(Wilder, et al., 2002). Some of the factors that lead to the development of HAVS are

characteristics of the vibrating tool (vibration magnitude, direction and frequency; and

duration of tool use), the type and condition of the tool, environmental factors, biodynamic

factors, ergonomic factors, and individual factors (ISO 5349-1, 2001).

There has been extensive research conducted on vascular disorders associated with

vibrating tools. NIOSH published a document in 1997 that provided a critical review of

epidemiological evidence associated with Hand Arm Vibration Syndrome (Bernard, 1997).

From 20 epidemiological studies, Bernard concluded that “there is substantial evidence that

as intensity and duration of exposure to vibrating tools increase, the risk of developing

HAVS increases” (1997, p. 5c-9).

In addition to VWF, Carpel Tunnel Syndrome (CTS) has also been linked with

exposures to hand-transmitted vibration, however, not by itself (Bernard, 1997). Mild

numbness and tingling is common in both HAVS and CTS. But the vascular injury to the

hand in hand-transmitted vibration is different than the nerve compression in CTS

(Pelmear & Leong, 2000).

Disorders associated with hand-transmitted vibration are not only linked to the

vascular system of the hand but also there is evidence with chronic problems with bone and

8

joints, peripheral neurological system, muscular system of the hand, among other disorders

(Griffin, 1990). The mechanisms for each of the disorders is also not clearly understood

(Pelmear et al., 1992).

Diagnosis of Hand-Transmitted Vibration Disorders

There is no definitive, objective diagnostic test for the vascular disorders

associated with hand transmitted vibration (NIOSH, 1989). Physicians rely on the

subjective report from the worker. This makes the diagnosis and classification difficult

for the physicians (NIOSH, 1989). Although none of the diagnostic tests for vascular

disorders due to hand transmitted vibration are considered the “gold standard,” some of

these tests can be useful in the assessment in conjunction with the subjective medical

evaluation (Griffin, 1990, p. 592). Some of the diagnostic tests include: Doppler studies,

plethysmography, finger systolic pressure measurements. There are also similar

diagnostic tests for sensineural effects (Physical and Biological Hazards, Wilder, 2002).

The medical community has devised assessment methods to determine the degree

of HAVS once it is diagnosed. In 1968, Taylor and Pelmear devised a classification system

that was used until 1986 when their classification system was modified by the Stockholm

Scale (Wasserman, 2001). The Stockholm Scale separated vascular and sensineural effects

and also evaluated both hands (Pelmear, et al., 1992). The three scales are found in Tables

1 through 3.

9

Table 1. Taylor–Pelmear Stages of VWF (Pelmear et al., 1992, Table 3-1, p. 28)

Stage Condition of Digits Work and Social Interference 0 No blanching of digits No complaints.

OT or ON Intermittent tingling, numbness, or both.

No interference with activities.

1 Blanching of one or more fingertips with or without tingling and numbness.

No interference with activities.

2 Blanching of one or more fingers with numbness; usually confined to winter.

Slight interference with home and social activities. No interference at work.

3 Extensive blanching. Frequent episodes, summer as well as winter.

Definite interference at work, at home, and with social activities. Restriction of hobbies.

4 Extensive blanching; most fingers; frequent episodes, summer and winter.

Occupation changed to avoid further vibration exposure because of severity of symptoms and signs.

Table 2. Stockholm Workshop Scale for the Classification of Cold-Induced Raynaud’s Phenomenon in

HAVS (Pelmear et al., 1992, Table 3-2, p. 29)

Stage Grade Description 0 No attacks 1 Mild Occasional attacks affecting only the tips of one or more fingers 2 Moderate Occasional attacks affecting distal and middle (rarely also

proximal) phalanges of one or more fingers 3 Severe Frequent attacks affecting all phalanges of most fingers 4 Very severe As in stage 3, with trophic skin changes in the fingertips

Table 3. Stockholm Workshop Scale for the Classification of Sensorineural Effects of HAVS (Pelmear et

al., 1992, Table 3-3, p. 29)

Stages Symptoms 0SN Exposed to vibration but no symptoms 1SN Intermittent numbness, with or without tingling 2SN Intermittent or persistent numbness, reduced sensory perception 3SN Intermittent or persistent numbness, reduced tactile discrimination and/or

manipulative dexterity

Physics and Terminology

In order to understand how vibration affects the body and how vibration is

measured, it is important to understand some of the physics and terminology involved

with vibration. For the purposes of this discussion, vibration is the oscillatory movement

of a solid or tool; the motion can be periodic (sinusoidal) or random, and either

10

intermittent or continuous (Soule, 1973). “The simplest form of periodic vibration is

called pure harmonic motion which is a function of time and that can be represented by a

sinusoidal curve” (Soule, 1973, p. 339). Three components are related mathematically to

pure harmonic motion: displacement from an equilibrium position, velocity or rate of

change in displacement, and acceleration or vector quantity expressed as rate of change in

velocity (Bruce et al., 2001). Acceleration is the critical component when considering

occupational vibration measurement since it believed that the force from the acceleration

is responsible for adverse health effects (Bruce et al., 2001). Equation 1 represents

acceleration mathematically.

a = -ω2X sin(ωt) = apeaksin(ωt) (1)

Where: a = acceleration (m/s2) apeak = maximum acceleration

f = frequency (Hz or cycles/s) t = time (s) ω = angular frequency or 2πf

X = maximum displacement (m) *adapted from The Industrial Environment: Its Evaluation and Control, NIOSH, 1974, p. 339

Vibration is defined as a vector quantity; it has magnitude and direction

(Wasserman, 2001). Describing occupational vibration exposure levels is difficult. Peak

vibration levels are useful when the waveform is purely sinusoidal; however, most

occupational vibrations are not pure sinusoid waveforms and are complicated with

varying frequencies (Bruce et al., 2003). Root-mean-square (rms) values are the primary

unit for occupational vibration because the rms values are proportional to the energy

content of the vibration (Soule, 1973). Root-mean square values were the preferred

method to describe severity of HTV exposures; it was a common measure in engineering

fields and was a convenient term for measurement and analysis (Griffin, 1990). Root-

mean-square acceleration for an ISO frequency-weighted, single axis is defined in

Equation 2 below:

( )dttaT

aT

rmshw hw∫=0

2)(

1 (2)

Where: a is the rms single axis acceleration of the ISO frequency-weighted hand-transmitted

vibration in m/s2

t is time in seconds T is the measurement time period.

*from ANSI S2.70-2006,(2006, Eq. 3, p. 4)

The direction component of vibration transmitted to the hand is described in three

directions (x, y, and z) of an orthogonal coordinate system. Additionally, vibration is also

transmitted through rotational axes: pitch, roll and yaw. The linear axes (x, y, and z) are

used and explained by two coordinate systems typically associated with hand transmitted

vibration: biodynamic and the basicentric coordinate systems. The biodynamic system is

referenced from the third metacarpal of the hand and defines motions in x, y, and z axes

(Wilder et al., 2002). Measurements for occupational vibration are not traditionally

obtained directly from the hand but are taken from the tool handle, making the tool the

reference point for the basicentric coordinate system (See Figure 1). It is an

approximation of the biodynamic coordinate system.

11

Figure 1. Description of Biodynamic and Basicentric Orthogonal Coordinate Axis Systems (diagram from

ANSI S2.70-2006, Figure 1(a), p. 6)

In 2001, the ISO 5349 (1986) was revised to change reporting requirements from a

dominant, ISO frequency-weighted, single axis acceleration to a root sum of squares

acceleration (ahv) (ISO 5349-1, 2001). The European Union Directive (2002) followed

by requiring the measurement and reporting criteria of the ISO 5349 (2001). In 2006,

ANSI updated their 1986 standard for hand-transmitted vibration to meet the

measurement and reporting criteria of the ISO 5349 standard (2006). The current

ACGIH TLV (2006) and the NIOSH Criteria Document (1989) for hand-transmitted

vibration both still use the dominant, ISO frequency-weighted, single-axis measurements.

The vibration generated by the tool has direction and is quantifiable, but the

direction and magnitude also vary with the frequency component of the vibration

transmitted to the hand. The vibration frequency unit is expressed in Hertz (Hz). A

frequency weighting has been used in several vibration standards and is based on

subjective sensations tolerated at varying frequencies (Griffin, 1997). The frequencies

12

evaluated ranged between 10 and 300 Hz for hand-transmitted vibration (NIOSH, 1989).

The frequency weightings currently used in ANSI, ACGIH, and ISO have been

extrapolated from the vibration sensations and are not health based (Griffin, 1997). The

frequency range for each of the standards (ISO 5349-1, 2001; ACGIH, 2006; & ANSI

S2.70, 2006) is between 5.6 and 1400 Hz. The composite frequency weighting used for

hand-transmitted vibration by ANSI, ISO and ACGIH has not been linked to any one

specific disorder; however there are certain frequencies have been linked to specific

disorders (Griffin, 1990). The frequency weighting is illustrated below in Figure 2.

Figure 2. Frequency weighting used by ANSI, ISO, and ACGIH (From ISO 5349-1:2001(E), Figure A.1, p. 9).

The NIOSH Criteria Document for HAV (1989) disagreed with the frequency

weighting and suggested that it underestimates the health effects produced from the high

frequencies (NIOSH, 1989). NIOSH (1989) also goes on to state that unweighted

frequency acceleration values provides a better means of assessing health risk with hand-

13

14

transmitted vibration. Bovenzi (1998b) indicated that there is not enough evidence to

support the theory that unweighted acceleration values are a more representative measure

of risk for vascular disorders than the ISO frequency-weighted accelerations.

Another topic important to the understanding of occupational vibration is the

concept of resonance. Wasserman (2001) defines resonance as “the tendency of a

mechanical system (or the human body) to act in concert with externally generated

vibration and to internally amplify the input vibration and exacerbate its effects” (Chapter

105, Section 1.6, para. 1). The maximum acceleration can be transmitted to the hand-

arm system at its resonant frequency. The resonant frequency range of the hand-arm

system is between 150 – 300 Hz (Bruce et al., 2003).

Since the acceleration levels are gathered from the tool, an important question

must be answered: how much is energy is absorbed by the hand? Several factors affect

how the vibration is transmitted to the hand and fingers which includes the vibration

magnitude, direction, and frequency, hand coupling to the tool, hand-arm posture,

environmental conditions, and duration of exposure (Griffin, 1990, p. 609). There is still

a tremendous amount information that must be discovered to fully understand how

vibration causes injury.

Occupational Standards and Guidelines for Hand-Transmitted Vibration

Several organizations have put forth health and safety standards or guidelines for

the control of the vibration produced by powered hand tools. The United States has

published the following guidance on hand-transmitted vibration:

• ACGIH TThreshold Limit Value for Hand-Arm Vibration, 2006,

15

• ANSI S2.70-2006 American National Standard Guide for the Measurement and Evaluation of Human Exposure to Vibration Transmitted to the Hand and,

• NIOSH Criteria For a Recommended Standard: Occupational Exposure to Hand-Arm Vibration, 1986.

The U.S. Occupational Safety and Health Administration (OSHA) has not

developed regulatory standards for the control of HAV.

The American Conference of Governmental Industrial Hygienists (ACGIH)

developed a threshold limit for hand-transmitted vibration that ACGIH believes that will

protect nearly all workers from progressing to Stage 1 of the Stockholm Workshop Scale

for the Classification of Cold-Induced Raynaud’s Phenomenon in HAVS (see Table

2)(ACGIH, 2006). The ACGIH guideline requires that measurements be collected in

accordance with ISO 5349 (1986) or ANSI S3.34 (1986). Both the ISO 5349 (1986) and

the ANSI S3.34 (1986) standards are based on the dominant axis, frequency-weighted,

rms accelerations. Both the ISO and ANSI standards have been revised in 2001 and

2006, respectively considers root sum of squares for each of the three basicentric or

biodynamic axes.

Guidance for hand-transmitted vibration in the United States Navy sailors is

found in OPNAV Instruction 5100.23G (2005). The U.S. Navy guidance document

instructs personnel to refer to the ACGIH TLV for Hand-Arm Vibration (2006) for two

exposure scenarios. The first is for high vibration tools, such as, percussive-type tools

(impact wrenches, carpet strippers, chain saws), percussive tools (jack hammers, needle

scalers/guns, riveting or chipping hammers), and other high vibration tools where the

usage exceeds 30 minutes total per day. The second is for moderate vibration tools such

as, grinders, sanders, jigsaws, where the usage exceeds 2 hours total per day.

16

ANSI recently updated the standard for hand-transmitted vibration in May 2006:

American National Standard – Guide for the Measurement and Evaluation of Human

Exposure to Vibration Transmitted to the Hand, ANSI S2.70-2006. The ANSI standard

is very similar to the current ISO 5349 (2001) and European Commission (2002)

standards in that it requires the determination of the root sum of squares, frequency-

weighted, rms acceleration (ahv). The ANSI S2.70 standard (2006) also identifies both

parts of the ISO 5349 (2001) and ISO 8041 (2005) (Human Response to Human

Vibration – Measuring Instrumentation) as “indispensable for the application” of the

ANSI S2.70 standard. One difference between the ISO 5349 (2001) and the ANSI S2.70

standard (2006) is that new ANSI standard prescribes a Daily Exposure Action Value

(DEAV) and a Daily Exposure Limit Value (DELV). Each of the values are based on an

eight hour work day where the DEAV is equal to 2.5 m/s2 and the DELV is equal to 5.0

m/s2. The DEAV represents a point at which symptoms of HAVS may begin to appear

and the DELV are expected to be at high risk for developing HAVS (ANSI, 2006). The

ANSI standard (2006) also presents a plot, Figure 3, which illustrates the location of the

health risk zones based on duration of tool use and the root sum of squares acceleration

value (ahv).

Figure 3. ANSI Health Risk Zones for DEAV and DELV (ANSI S2.70-2006, Figure A.1, p. 12) In the international community, the International Organization for Standardization

(ISO) has developed a consensus standard for hand transmitted vibration:

• ISO 5349-1:2001 Mechanical vibration – Measurement and evaluation of human exposure to hand-transmitted vibration – General Requirements

• ISO 5349-2:2001 Mechanical vibration – Measurement and evaluation of human exposure to hand-transmitted vibration – Practical guidance for measurement at the workplace

The ISO 5349 (1986) was changed in 2001 to measure the root sum of squares for

the x, y, and z axes acceleration values instead of reporting the rms acceleration of the

dominant axis. The new ISO 5349 standard (2001) recognized that not all power tools

are dominated by a single direction of vibration magnitude.

The current ISO standard for exposures to hand-transmitted vibration, ISO 5349

(2001), is divided into two parts. Part 1 provides information on the health effects related

to hand-transmitted vibration, the relationship between vibration exposure and effects on

17

health, factors likely to influence the effects of human exposure to hand-transmitted

vibration in working conditions, and specific guidance on preventative measures for hand

transmitted vibration. Part 2 gives specific guidelines on how to measure vibration on

hand-held vibrating and percussive tools. This standard takes into consideration the

frequency of the vibration, magnitude, duration of exposure per day and the cumulative

exposure to date (ISO 5349-1, 2001). However, the ISO 5349 (2001) standard does not

prescribe a safe limit for hand-transmitted vibration exposures. The standard does

indicate that the information it provides “should protect the majority of the workers

against serious health impairment associated with hand-transmitted vibration” (ISO 5349-

1, 2001, p. vi)

Although the ISO 5349 standard does not provide occupational exposure limits, it

does provide a way of predicting 10% prevalence of HAVS in a population that uses

vibrating hand tools. The ISO 5349 standard (2001) indicates that Equation (3) below

“can be used to define exposure criteria designed to reduce the health hazard of hand

transmitted vibration in a group of occupationally exposed persons” (p. 16). For

example, an eight hour daily exposure of 10 m/s2 would indicate that 10% of that

particular exposed group would develop finger blanching or HAVS in 2.77 years.

06.1)8(8.31

ADy = (3)

Where A(8) is the daily vibration exposure and Dy is the group mean total (lifetime) exposure in years *from ANSI S2.70(2006, Eq. A.4, p. 13)

18

The ISO 5349-2 standard describes guidance on the measurement methods and

data collection. Both the ANSI S2.70 standard (2006) and the NIOSH Criteria Document

(1989) provide information regarding measurement and data collection.

The Europeans have recently taken a step forward in setting a regulatory health

standard for hand-transmitted vibration that includes exposure limits. All countries part

of the European Commission were required to comply with the requirements set forth in

the European Directive 2002/4/EC (2002) regarding the minimum requirements for

protecting the health of workers from hand transmitted vibration by July 6, 2005. The

European Directive prescribes a daily Exposure Action Value (EAV) and a daily

Exposure Limit Value (ELV). Both the EAV and the ELV consider time of exposure.

The 8-hour acceleration value for the EAV is 2.5 m/s2 and for the ELV it is 5.0 m/s2

(European Directive, 2002). The equations for calculating the EAV and the ELV based

on time are described below with Equation (4) and (5), respectively (Griffin, 2004).

21

haction

85.2 ⎥⎦

⎤⎢⎣

⎡=

ta (4)

21

hlimit

80.5 ⎥⎦

⎤⎢⎣

⎡=

ta (5)

Where th is the exposure duration express in hours.

The ELV and EAV have also been adopted by the new ANSI S2.70 Standard (2006).

The European Directive requires measurements to be collected in accordance with ISO

5349-1 (2001).

Griffin (2004) and the new ANSI S.2.70 (2006) standard use an equation from

ISO 5349, Equation (3) above, to predict HAVS in 10% of a population exposed to

19

20

vibration of the hand for the EAV and the ELV values of the European Directive. There

is a 10% chance of HAVS for an ELV exposed worker in 5.8 years and 12 years for the

EAV.

Hand-Transmitted Vibration Measurements

The test tool for the study was a compressed air-powered needle gun. The needle

gun is considered a percussive tool and measurement challenges are associated with these

types of tools. The ISO 5349-2 standard (2001) gives practical guidance in measurement

collection.

The ISO 5349-2 standard (2001) suggests the following considerations when

collecting measurements with percussive tools: proper selection of accelerometer, proper

placement of the accelerometer, proper connections between the vibration instrument and

the accelerometer, and placement of the cable. The ISO 5349-2 standard (2001) also

suggests that a mechanical filter be used with percussive tools that should not alter the

frequency response characteristics of the instrumentation. The filter is to be used to reduce

high frequencies and prevent mechanical overloading of the integrated circuit piezoelectric

accelerometer (ISO 5349-2, 2001).

ISO 5349-2 (2001) suggests that the selection criteria for the accelerometer should

allow it to tolerate the range of anticipated vibration magnitudes and have stable

characteristics. The accelerometer should also be stable in the environment (i.e.,

temperature, humidity) tested and the weight should not interfere with the vibration

characteristics of the tool.

Placement of the accelerometer is also important and can vary. The ISO 5349-2

standard (2001) recommends that placement of the accelerometer be at or near the surface

21

of the hand near the vibration entry point of the hand or near the middle of the palm. In

most practical cases, the accelerometer cannot be placed on the hand without interfering

with the worker’s grip on the tool. The accelerometer should be placed near either side of

the hand from the grip position (ISO 5349-2, 2001).

There are also various ways to mount the accelerometer to the tool. The most

common method is to securely tighten a clamp around the accelerometer and tool. There

are other ways of securing the accelerometer on the tool as well: screwed or welded

mountings, glue or adhesive mountings, clamp mountings, hand-held adaptors (ISO 5349-

2, 2001).

Another important aspect in the measurement of hand-transmitted vibration

concerns the cable between the accelerometer and the instrument. If the cable is not

secured to the vibrating surface near its connection, this may cause interference with the

measurement. Additionally, improper or faulty connections between the cable,

acceloremeter, and the instrument can also contribute to unreliable acceleration values (ISO

5349-2, 2001).

Other possibilites for measurement error include DC-shifts. Griffin (1990)

describes this phenomenon as “an erroneous instantaneous change in the DC signal

produced by some accelerometers and their signal conditioning in response to mechanical

shock” (p.811). The ISO 5349-2 standard (2001) states that the DC-shift can occur in the

accelerometer and cause a mechanical overloading of the piezoelectric electronics. The

ISO 5349 standard for hand-transmitted vibration indicate that a mechanical filter should be

used between the accelerometer and the percussive tool. The ISO 5349-2 standard (2001)

cautions the user that the mechanical filter may increase the accelerations of the non-

22

percussive axes. Smeatham, Kaulbars, and Hewitt (2001) suggest that a thin sheet of

resilient material will suffice to reduce the DC-shift with lightweight accelerometers; less

than two grams.

Studies Associated with Needle Scalers and Hand-Transmitted Vibration

There are few studies on the characterization of needle scalers with regard to

vibration. The British Human Factors Research Unit, Institute of Sound and Vibration

Research, and Medical Research Council evaluated vibration associated with several

different types of tools in 1999 (Paddan, Haward, Griffin, & Palmer). This study evaluated

vibration by using a finger ring that was held securely against the tool and fitted with three

separate accelorometers to measure each of the mutual orthoganol axes (Paddan et al.,

1999). The researchers sampled for a five second period and used the ISO 5349 (1986)

frequency-weighting for the measurements. The study gathered 10 triaxial measurements

from three needle scalers. The dominant axis was determined to be the y axis (percussive

axis) for all but one measuement from the needle scalers. This study also included a

spectral analysis of the acceleration across the frequency range evaluated. Pressure from

the compressor supplying air to the tool was not noted in the survey. The researchers

calculated the root sum of squares (rss) for all ten measurements. The mean rss

accelerations for tools 1 and 2 in the cleaning modes was approximately 17 m/s2. The

results of this study are summarized below in Table 4. The rss values in Table 4 for the x,

y, and z axes were not part of the report; but were calculated for comparison purposes to the

data collected for this research study.

23

Table 4. Needle Gun Vibration Measurements from HSE Contract Research Report 234/1999

Frequency-weighted Vibration Accelerations (rms m/s2) Tool # Operation Handle x y z rss

free run main body 4.31 18.77 3.89 19.65 cleaning main body 3.99 13.35 6.48 15.37 cleaning main body 4.70 12.77 3.73 14.11

1

cleaning main body 4.05 12.64 4.94 14.16 free run main body 2.71 23.03 3.21 23.41 cleaning main body 4.81 18.62 5.78 20.08 cleaning main body 3.33 18.31 5.32 19.36

2

cleaning main body 2.49 18.21 3.90 18.79 cleaning rear 4.40 10.90 14.50 18.67 3 cleaning main body 2.50 28.70 2.60 28.93

*adopted from Paddan et al, 1999, Table B1, p. 48.

This study recommended that measurements for hand-transmitted vibration should

include direct measurement of vibration magnitudes, documentation of tool use and

duration patterns, and ergonomics in the workplace (Paddan et al., 1999).

Palmer, Coogon, Bendall, Kellingray, Pannett, Griffin, and Haward (1999),

conducted a postal survey in Great Britain to determine occupational exposures to

vibration. The study determined personal vibration exposures based on ahw (dominant,

frequency-weigthed, single-axis) values from published and other sources of information.

The study determined the dominant rms single-axis acceleration value for needle scalers

was 16.0 m/s2.

Some tool manufacturers (Trelawny SPT Ltd. (2006), Chicago Pneumatic (2006),

and Jet Tools (2006)) list the acceleration levels for their equipment in a specification sheet

or on their web sites. The three listed manufacturers indicate that they use the ISO 8662-14

standard (1996) for the measurement of their needle guns. The ISO 8662-14 is the specific

guidance used in determining vibration levels with needle guns in laboratory-type

controlled conditions. The requirements of the ISO 5349-1 standard (2001) gives more

24

latitude as how to collect and document the vibration levels. Trelawny SPT Ltd. (2006),

Chicago Pneumatic (2006), and Jet Tools (2006) website posted acceleration values for

needle scalers can range from less than 10 to nearly 25 m/s2.

Study Objectives

The principal purpose of this study was to assess the vibration level of a typical

needle gun used by the U.S. Navy in the free and contact modes. A second objective was

to examine the effects of tool supply air pressure on vibration. The null hypotheses for this

study were:

• Tool supply air pressure does not affect vibration

• There is not a difference in vibration levels between contact and no contact with a surface

METHODS

Materials and Equipment

The test needle gun for this study was the Taylor Pneumatic Tool Company

needle scaler (Model No.: T-7356). The needle scaler was borrowed from new stock of

a U.S. Navy ship’s tool issue. The Taylor needle scaler is a cylindrical-shaped tool that is

15 inches long, weighs 6 pounds and is shown in Figure 4. The manufacturer of the

needle scaler states that the tool operates at 4500 blows per minute (bpm) which can be

converted to a fundamental frequency of 75 Hz. The needle scaler manufacture literature

indicates that 10 cubic feet per minute (cfm) is required to operate the tool at 90 pounds

per square inch (psi) and not to operate the tool above 90 psi. A 50 foot section of rubber

hose was connected between the air compressor and the tool. The hose was uncoiled to

prevent restrictions on air flow.

A Mi-T-M Corporation single stage air compressor (Model No.: AC1-PH55-08M)

was used to power the needle gun. The specifications for the air compressor indicate that

9.0 cfm of air can be delivered at 100 psi. Part of the reason for selecting 80 and 60 psi

was for sustained air flow to the tool.

Figure 4. Taylor Pneumatic Tool Company, Needle Scaler, Model T-7356

25

Vibration Measurement Instrumentation

The Quest Technologies HAVPro personal human vibration monitor was used for

the data collection. The HAVPro vibration kit comes with a tri-axial, integrated circuit -

piezoelectric (ICP) accelerometer manufactured by PCB Group, Inc. (Triaxial PCB ICP®

Model 356A67).

Due to mounting limitations on the Taylor needle scaler, the tri-axial

accelerometer was mounted on the tool such that the actual basicentric “Y” (percussive)

axis was the “X” axis on the mounted accelerometer and illustrated in Figures 5a-c. The

mounted Z axis is the X axis on the basicentric coordinate system and mounted Y is the

basicentric Z axis. See Figure 1 for comparative purposes.

Y axis

Z axis

(a) (b) (c) Figure 6. Illustration of Accelerometer Mounting. (a) Photo of tool grip of hand and mounted accelerometer. (b) Photo of the ICP accelerometer mounted onto the needle scaler. X axis runs parallel to tool handle and would be considered the Y axis on the basicentric coordinate system, (c) illustration of all three axes on the ICP accelerometer.

Two 1/16” rubber gaskets (as a double layer) were installed between the tool and

the accelerometer and another 1/16” piece of rubber was wrapped around the hose clamp

illustrated in Figures 5a and 5b. This provided the mechanical filter as suggested by the

ISO 5349-2 standard. The filters are used to lower measurement errors by reducing the

high acceleration in the higher frequencies and “prevents the overloading of the

26

27

piezoelectric system” (ISO 5349-2, 2001). The specifications for the PCB ICP

accelerometer and Taylor needle scaler are provided in Appendix A and B, respectively.

The tool-mounted accelerometer was connected to the Quest Technologies

HAVPro instrument by way of a shielded cable. The cable was taped to the tool and to a

small length of the hose to reduce a triboelectric effect.

The HAVPro meets requirements of the ISO 8041:1990(E) Human response to

vibration – Measuring instrumentation. Since the HAVPro meets the requirements for

ISO 8041, the instrument is compatible with ISO Standards 5349-1:2001 and 5349-

2:2001.

Protocol

Five test subjects held the needle scaler in three conditions: 1) idle, in hand, 2)

activated, in hand, and 3) activated on a cast iron manhole cover. The idle condition was

conducted one time for each test subject. Each of the other two conditions was conducted

for twenty seconds and each condition was repeated three times. Conditions #2 and #3

were repeated at two different air pressures: 60 and 80 pounds per square inch (psi). The

pressures used in this research were in accordance with the manufacturer’s

recommendations of less than 90 psi.

A total of 13 measurements were collected for each subject. The HAVPro

instrument was setup to average in 1 second intervals for the x, y, z axes and the root sum

of squares (ahv). Prior to each measurement, the instrument was allowed to stabilize for

approximately twenty seconds. The data was stored onto the HAVPro and then

downloaded to a laptop computer which interfaced with the QuestSuite Professional,

Version 1.70 software package.

28

The data from the QuestSuite were then exported into Microsoft Excel and

formatted for analysis. Each of the thirteen 20-second samples per individual was

converted to a root-mean-square (rms) value by Equation 2. The rms acceleration values

for the root sum of squares (x, y, and z axes) were then analyzed with the JMP IN 5

statistical software (SAS Institute, Cary, NC) using an analysis of variance (ANOVA)

and providing descriptive statistics. Significant differences were considered to exist

when the probability of a Type I error was less than 0.05. A multiple comparison

procedure, Tukey’s Honestly Significant Difference (HSD) test, was used in a further

statistical analysis.

29

RESULTS

The primary purpose of this study was to characterize hand-transmitted vibration

of one needle scaler used by U.S. Navy sailors. ISO frequency-weighted, rms (root-

mean-square) acceleration levels were measured on the needle scaler with five subjects,

two different pressures (60 and 80 psi), and measurements were gathered when the tool

was activated and in contact with a surface and not in contact with a surface. An

additional twenty second condition was evaluated when the tool was not activated in the

subject’s hand. The output from the HAVPro instrument provided an averaged rms

acceleration level at each second for each of the three axes (x, y, and z) and the root sum

of squares (ahv) of the three axes. The order of exposures for each subject is listed below

in Table 5. Subjects were measured in the order listed (left to right) and then from top to

bottom. The rms acceleration levels for ahv from each 20-second sample and the means

and standard deviations are summarized below in Table 6.

Table 5. Order of Exposures

Test # Subj 1 Subj 2 Subj 4 Subj 5 Subj 3 1 R R R R R 2 80NC 60C 60NC 80C 60NC 3 80C 60NC 60C 80NC 60C 4 80NC 60C 60NC 80C 60NC 5 80C 60NC 60C 80NC 60C 6 80NC 60C 60NC 80C 60NC 7 80C 60NC 60C 80NC 60C 8 60C 80NC 80C 60NC 80C 9 60NC 80C 80NC 60C 80NC

10 60C 80NC 80C 60C 80C 11 60NC 80C 80NC 60NC 80NC 12 60C 80NC 80C 60NC 80C 13 60NC 80C 80NC 60C 80NC

R = tool resting in hand, not activated 60 or 80 = pressure in psi C = tool activated and in contact with surface NC = tool activated in hand, no contact with surface

30

Table 6. Summary of ahv for All Subjects, Trials, Pressure (60 & 80 PSI), and Contact/No Contact

60 PSI 80 PSI Tool Idle

No Contact Contact No

Contact Contact Not Activated

Subject Trial ahv (m/s2) ahv (m/s2) ahv (m/s2) ahv (m/s2) ahv (m/s2) 1 13.7 10.7 15.2 13.0 2 13.6 11.6 15.5 12.5 1 3 13.7 11.7 15.5 12.6

0.143

1 13.9 11.1 15.9 12.9 2 13.9 11.8 16.1 13.4 2 3 13.7 11.5 16.0 12.8

0.195

1 14.1 11.4 16.9 13.0 2 14.3 11.8 16.8 12.9 3 3 14.2 11.9 16.8 13.4

0.151

1 13.7 11.7 15.5 13.2 2 14.1 11.6 16.3 13.8 4 3 13.9 12.3 16.9 13.2

0.261

1 14.1 11.3 17.1 14.1 2 14.2 10.8 17.3 12.6 5 3 13.9 11.4 17.1 13.0

0.137

Means 13.9 11.5 16.3 13.1 0.177 Standard

Deviations 0.219 0.421 0.697 0.450 0.052

A three-way ANOVA (subjects by pressure by contact) with replicates (not

including idle conditions) was conducted on the data. The analysis included the main

effects and the interaction of pressure and contact. The subjects were treated as a

blocking variable. All the main effects and the interaction were significant at p<0.001.

Tukey’s HSD test was used to determine which pairs were significantly different among

the interaction pairs. Each interaction pair was significantly different at p<0.001 level.

The interaction of pressure and contact shows the amount of increase in acceleration

levels from 60 to 80 psi in the contact mode is greater than the increase in acceleration

levels when the tool was not in contact with a surface.

31

DISCUSSION AND CONCLUSIONS

The main purpose of this study was to provide data on vibration associated with

the use of a needle gun used by U.S. Navy sailors. The vibration of the Taylor T-7356

needle gun was evaluated at two pressure levels and contact conditions.

Significant differences in vibration were noted with change in pressure and

between contact with a surface and no contact. The measured mean acceleration levels

for the Taylor needle gun in contact with a surface were 11.5 and 13.1 m/s2 at 60 and 80

psi, respectively. The mean accelerations without contact were 14.0 and 16.3 m/s2 at 60

and 80 psi, respectively; with increased vibration over contact of 2.5 and 3.2 m/s2.

Two British reports (Palmer et al., 1999. and Paddan et al., 1999) identified

differences in accelerations in the contact and no contact modes. The first study, Palmer

et al. (1999), determined that 16.0 m/s2 was the dominant, single-axis acceleration

representative for needle guns in Great Britain. The root sum of squares value (ahv)

would be slightly higher than the dominant single axis value.

The second study, (Paddan et al., 1999) evaluated the acceleration levels of three

needle guns used in Great Britain. The Paddan et al. (1999) study mean root-sum of

squares (rss) accelerations for tools #1 and #2 were 14.6 and 19.4 m/s2 in the

contact/cleaning mode and 19.7 and 23.4 m/s2 in the non-contact mode, respectively.

Tool #3 appeared to be a gun-type needle scaler and there were two measurements (two

different handles) for this particular tool in the cleaning mode. It should be noted that

neither of the two British studies indicated the tool supply air pressure. The acceleration

levels determined by the British were higher than the values found in this research; and

32

the Paddan et al. (1999) study demonstrated similar differences between accelerations in

the contact and no contact modes.

Some tool manufacturers; such as Trelawny SPT Ltd.(2006), Chicago Pneumatic

(2006), and Jet Tools (2006), provided acceleration data on their needle scalers.

Trelawny SPT Ltd. (S. Jerger, personal communication, July 11, 2006) and Chicago

Pneumatic (T. Wastowicz, personal communication, July 13, 2006) indicated they used

the ISO 8662 standard for measuring acceleration levels. Jet Tools (2006) just listed the

vibration acceleration levels on their web site and did not indicate what method was used

to determine the acceleration levels. The ISO 8662-14 standard (1997) for needle guns

requires a controlled environment for acceleration measurements. Chicago Pneumatic

had several cylindrical needle scalers in their inventory and the accelerations ranged from

3.7 to 16.9 m/s2 (Chicago Pneumatic, 2006). Trelawny SPT Ltd. had two different

cylindrical needle scalers, models 1B and 2B, that had vibration acceleration levels at 8.5

and 9.3 m/s2, respectively (Trelawny SPT Ltd., 2006). The specifications for Taylor

needle scaler used in this research did not provide acceleration data.

There was some lack of uniformity in currently available measurement standards,

at least between the two ISO standards, 8662-14 (1996) and 5349 (2001). Tool

manufacturers use the ISO 8662-14 (1996) to provide acceleration data for needle guns

new tools where the ISO 5349 (2001) method is used for more measuring vibration levels

for tools used in the workplace. Both the NIOSH Criteria Document on Hand-Arm

Vibration (1989) and the work of Wasserman, D. E., Hudock, Wasserman, J. F.,

Mullinix, Wurzelbacher, and Siegfried (2002) suggested that newer tools will have lower

33

vibration levels than tools that have been used during normal operations over time and/or

poorly maintained.

One outcome that both the Paddan et al. (1999) or Palmer et al. (1999) studies did

not evaluate was the effect of tool supply air pressure on vibration. The current research

found that increasing pressure increases vibration levels. Adjusting tool supplied air

pressure to a minimum level while maintaining tool function can be used as control

measure to reduce the acceleration transmitted to the hand. Although, reducing the

pressure may increase the amount of time to complete the job with the tool; thereby

increasing time of vibration. The current research also demonstrated that the acceleration

values were higher in the no-contact mode versus the contact mode.

The mean acceleration values for 60 psi, contact with a surface and 80 psi, contact

with a surface were 11.5 and 13.1 m/s2. Based on the means at the two pressures and

with the needle scaler in contact with a surface, the EAV and ELV times for 60 psi would

be 23 and 91 minutes, respectively. The EAV and ELV times for 80 psi are 18 and 70

minutes, respectively.

Navy sailors may use the needle scaler, worst case conditions, for four to five

hours in a day for a couple of months at a time. However, Navy use of the needle scaler

changes with rank. As sailors are promoted, the use of the needle gun either decreases or

ceases.

If a sailor were exposed at the 80 psi level of 13.1 m/s2 for four hours per day, the

daily exposure vibration level, A(8), would be 9.3 m/s2. Based on the group mean total

(lifetime) exposure equation (Equation 3), it would take 3 years or 650 working days for

this exposure group to present ten percent prevalence of HAVS. It does not likely appear

34

that HAVS would be prevalent in sailor populations because it is not likely that they will

use the needle gun for four hours per day for 650 days in their career. However, tool

pressure can be used to decrease accelerations to lower exposure levels.

In conclusion, the principal purpose of this study was to provide vibration data on

a needle gun used by U.S. Navy sailors. The results of the study revealed the following:

1. Vibration levels were higher in the no contact mode compared to the contact

mode,

2. Vibration levels increased as the tool supply air pressure increased and,

3. U.S. Navy sailors are not likely at significant risk for Hand-Arm Vibration

Syndrome for lifetime exposures to hand transmitted vibration.

Industrial workers are likely to remain on the same job using a number of

different vibrating tools longer than a U.S. Navy sailor. Industrial workers may likely be

at higher risk to vibration-induced white finger due to the increased lifetime exposures.

35

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APPENDIX A: PCB ICP ACCELEROMETER SPECIFICATIONS

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APPENDIX B: TAYLOR NEEDLE SCALER T-7356 SPECIFICATIONS

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